Vibration and sound damping outboard motor structure with extended shroud



Oct. 3, 1961 L. D. wATKlNs VIBRATIoN AND souND DAMPING ouTBoARD MoToRsTRUcTuEE WITH EXTENDED sHRouD Filed Jan. 1e. 1956 INVENToR. ua/u: L?Warn/v5 BY Ma, ,MM

States This invention relates to a vibration and sound damp- (not shown)for cooling the engine.

ing outboard motor structure with extended shroud.

The structure herein disclosed is an improvement upon that disclosed incompanion application 442,022 now U.S. Patent 2,740,368, iledvIuly 8,-1954 by Finn T. Irgens and me and entitled, Vibration and Sound DampingOutboard Motor Mounting.

'In the present device, as in the device of the companion application,there is a propulsion unit which comprises'the power head, gear casing,and connecting strut through which the drive shaft transmits power tothe propeller mounted on the gear casing. This unitary propulsion unitis not mounted directly to the transom bracket in accordance withconventional practice but is supported by springs which leave it freefor vibration in any direction. This, of itself, minimizes transmissionof noise and vibration to the boat. Further reduction in noise level inthe boat is achieved by enclosing the power head in a shroud. p

.'All previous attempts to bafile noise transmission from the power headto the boat by means of a shroud have either involved the mounting ofthe shroud directly fromv the propulsion unit or have involvedsupporting the shroud independently of the propulsion 'unit from thetransom bracket or the `steering pintle thereof.fr The present inventionmakes the shroud the primary element `which is dirigibly connected withthe transom bracket and supports the entire propulsion unit from theshroud so that the propulsion unit no longer has any connection with thesteering `pintle other than 'the connection through its spring supports,which are desirably elastomeric.

In the drawings:

FIG. 1 is a view of an'outboard motor embodying the 'invention partiallyin side elevation 'and partially in vertical fore and aft section.

FIG. 2 is a fragmentary view partially in rear elevation and partiallyiny vertical transverse -section through the outboard motor of FIG. 1.

FIG. 3 is a detail view taken in section on line 3--3 of FIG. 2.

The transmission bracket 5 may be conventionally designed forapplication to the transom 6 of a boat. In accordance with usualpractice, it has a bearing portion 7 connected to the clamp portion ofthe bracket by means of ar transverse pintle 8 upon which the bearingportion is movable in a vertical plane for accommodating tiltingmovement of the propulsion unit.

The bearing portion 7 has a kingpin 10 upon a generally upright axis,upon the upper and lower ends of which are mounted the ear portions 11and y12 of the shroud generally designated by reference character 15.Thus, the entire shroud is mounted to oscillate in a generallyhorizontal plane subject to the control of the tiller 16 connected toit.

Within the enlarged upper end portion 17 of the shroud is the power head18 of the propulsion unit. The power head usually comprises cylinders 19in which the pistons 20 are reciprocable, these being connected with thecrankshaft 2l, carrying vwheel magneto 22. The engine will desirably besupplied with fuel from some external source which may be as disclosedin U.S. Patent 2,656,828.

The portion 24 of the shroud extends downwardly to terminate very closeto the water line 25, and has a rtially in compression and partially inshear.

2 cross section materially reduced as compared with the cross section ofthe shroud portion 17 which houses the power head. Within the portion 24of the shroud is the vertical strut or shaft housing 27 through whichextends, the vertical drive shaft 28 and the usual water connectionsThestrut 27 is connected with gear housing 30, Within which there arethe usual gears shown in dotted lines in FIG. l, whereby power istransmitted from the drive shaft 28 to propeller shaft r31 which carriespropeller 32. Engine 17, strut 27 and gear housing 30 are connectedtogether as a rigid unit.

The propulsion unit is resiliently yieldably mounted in the shroud insuch a manner as to be movable respecting the shroud for vibration inany direction. The pre- L ferred means for effecting such mountingcomprises a pair of springs 32 which are desirably seated upon portionsof the shroud 33 which are downwardly diver-gent at opposite sides ofthe shaft housing portion 27 of the propulsion unit. These springs 32are below the power head 18, which provides seats at 34 for the upwardlyconvergent upper ends of springs 32.

While the invention is not particularly concerned with the type ofsprings employed, it is preferred that the springs be elastomeric, andit is appropriate to use cylindrical blocks` of oil resistant syntheticrubber as disclosed inthe companion application above identiiiedL Therubber blocks comprising springs 32 are vulcanized to mounting meanssuch as plates 35 and studs 36 whereby they are connected to theirrespective seats.

Al third spring r38 is disposed in a fore and aft plane. lf it is to be`under compression during" motor operation, it may be interposed betweenthe rear of strut 27 and the seat 39 provided in the shroud immediately.aft of the spring as shown in FIG. 1. As shown, the several springssupport the weight of the propulsion unit par- Torque vibration of thepropulsion unit about its neutral 'axis or about the axis of the driveshaft 28 is taken in shear. Propulsive thrust developed by the propeller32 and transmitted from the propulsion unit to the boat is largelyabsorbed at the lower end of the strut 27, but Vthe spring 38 will becompressed thereby and springs 32 will be subject to some such thrust inshear.

Springs 40 and 41, desirably also elastomeric,y are interposed betweenthe lower end of the strut 27 and the lower end of portion 24 of shroud15. These springs contribute shear to the support of the propulsion unitand to the positioning thereof within the shroud. Spring 40 is, ofcourse, the principal means of transmitting the thrust of the propulsionunit to the transom bracket and thence to the boat. Such propellerthrust is transmitted by spring 40 in compression and the springs 41cooperate by transmitting some of such thrust in shear Yin the preferredorganization of the parts wherein spring 40 is opposite the ear portion12 of they shroud at the point where the lower end of kingpin 10 isengaged thereby, as will clearly appear from FIG. 1 and FIG. 3. It isbecause the thrustr of propeller 32 is developed at a level considerablybelow the level of spring 40 that the rigid propulsion unit tends topivot somewhat upon spring 40 and to develop compression thrustagainstspring 38 at the upper end of such unit.

As more fully explained in the companion application above identified,all speed andy timing and reversing controls to the ypropulsion unithave to be mader flexible in order to accommodate the vibrationpermitted such unit by the vibration and sound absorbing mounting. -Notonly is the vibration damped before reaching lisent-d.. Oct.. 3.. 19stengine is also intercepted and largely kept from the boat by the shroudbecause of the extension of the shroud well below the top of transomand, desirably, to the immediate vicinity of the water line 25.

vIt will be noted that the tiller 16 is not connected with thepropulsion unit except through the shroud. It is the shroud whichbecomes that part of the outboard motor organization which is primarilyoscillated upon the axis of kingpin for steering purposes. Thepropulsion unit is constrained to follow the steering movement of theshroud solely by the transmission of steering motion through the severalvibration and sound damping springs.

Not only is the arrangement exceptionally elective in isolating the boatand its occupants from the vibration and noise of operation of thepropulsion unit, but the' structure shown is exceptionally simple ascompared with any other means of accommodating and damping enginevibration and at the same time supporting the shroud independently ofthe propulsion unit.

There is but one part pivoted upon the kingpin and that .is the shrouditself. The extension of the shroud downwardly about the shaft housingvor strut 27 makes possible both objectives in the simpliiication of thestructure and the dissipation of sound `waves at a point below thetransom and adjacent to the water.

I claim:

l. 'in an outboard motor, having a transom 'bracket and a propulsionunit including in unitary connection an engine having a depending driveshaft, a lower unit having a propeller and propeller shaft with whichthe drive shaft is in operative connection, and a strut housing thedrive shaft and connecting the engine and lower unit, the improvementwhich consists in a shroud substantially completely surrounding andspaced from said engine and adjacent portions of 4said strut andproviding a sound conning enclosure which vis complete to -a level materially closer to the lower unit than to said engine, means supportingthe shroud for steering oscillation, a tiller connected with the shroudfor directing the steering movement thereof, Aand vibration dampingsprings supporting the propulsion unit from the shroud to accommodatevibrations of said unit within the shroud lWhile Vconstraining said unitfor steering movement with the shroud.

2. The device of claim 1 in which the means supporting the shroud forsteering movement comprises a kingpin mounted on the transom bracket,the shroud having portions engaged with portions of the pin at the upperand lower end thereof for steering movement upon the axis of the pin.

3. In an outboard motor structure comprising a propulsion unit havinginsubstantial rigid connection a power head, strut and gear housing,.the gear housing being substantially `completely immersed in use to awater line adjacent the lower end of said strut, said power 'headincluding an engine having a ,dri-ve shaft connection through the strutto -a propeller shaft and propeller mounted on the gear housing, and atransom bracket applicable to a boat, and provided with. upright bearingmeans including a kingpin, the improvement consisting of a shroud havinga relatively large upper Aportion substantially completely enclosing thepower head of said unit and having a unitary downwardly .extendingttortion of reduced cross section substantially completely enclosing alarge part of the length -Qf the Strut Silbstantially to the lower endof the .strut and spaced from all parts of said propulsion unit, meansmoullllg $11.6 shroud upon the kingpin for steering oscillation aboutthe axis thereof, .a 'filler Connected with the .Shroud for controlling.steering movement thereof, `and resiliently yieldable means .forsupporting Said propulsion unit from the shroud to partake of .steeringmovement ,about the kugpin axis with the shroud, ,said propulsion unit'haring uo connection with the kngpinexcept through the shroud. and theshroud serving to confine to a level vnear the water line soundoriginating in the portions of said propulsion unit enclosed therein.

4. The device of claim 3 in which the means `4tor mounting thepropulsion unit from the shroud comprises a plurality of springsinterposed between said unit and said-shroud at .each of a plurality ofvertically spaced levels.

5. The device of claim 4 -in which at least one such spring is disposedbetween the shroud and said Vunit at the aPPlOXimate level of the lowerend of lthe Kingpin and in a vertical plane .extending fore and aftthrough said unit.

References Cited in the file of `this Ypatent 'UNITED STATES PATENTS2,166,234 Conover July 18, 41939 2,528,628 Whitney Nov. 7, 19502,555,548 Kiekhaefer June 5, 1951 2,585,774 Heidner et al. Feb. 12,1,952 2,740,368 4Irgens et al. Apr. 3, 19,56 .2,890,674 Rose June 16,1959

